This application relates to the overhaul of an existing gas turbine engine to provide a new gas turbine engine with a high overall pressure ratio across a pair of compressor sections.
Gas turbine engines are known and, typically, include a fan delivering air into a compressor as core airflow and delivering air into a bypass duct as bypass air for propulsion. The air is compressed in the compressor and delivered into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors, driving them to rotate and, in turn, drive the compressor and fan rotors.
It is typically the case that there are at least two turbine rotors, with a higher pressure turbine rotor driving a higher pressure compressor rotor and a lower pressure turbine rotor driving a lower pressure compressor rotor.
Historically, a fan rotor was driven at the same speed as a turbine rotor. In one type of gas turbine engine, this was at the same speed as the low pressure compressor and low pressure turbine. In a second type of gas turbine engine, a third turbine rotor drove the fan rotor.
More recently, the assignee of this application has developed gas turbine engines with a gear reduction placed between a turbine rotor and the fan rotor. This allows the fan rotor to rotate at slower speeds.
With this change, the bypass ratio can increase dramatically. This reduces the percentage of air being delivered as core airflow and puts a premium on the efficient use of the air being delivered into the compressor sections.
It is desirable to increase the pressure ratios across the low and high pressure compressor rotors. However, there are limitations in that the temperature at the downstream end of the high pressure compressor rotor cannot be unduly high due to material challenges.
As can be appreciated, a good deal of engineering expense goes into designing compressor sections. With the advent of next generation gas turbine engines including a gear reduction for driving the fan, there will be any number of new engines coming to market. This will require a huge amount of engineering design, testing, manufacturing, and expense to design new compressor sections.